The efficient excitation of elongated lasing (Nd:YAG, Nd:Glass, etc.) material by pump lamps has heretofore most efficiently been provided by spirally wrapping a tubular pump lamp about the length of the laser material or disposing the tubular pump lamp alongside the laser material and providing secondary focusing and/or diffusing material to efficiently couple the pump lamp generated excitation to the laser material. In all such applications, the pump lamp comprises a tubular housing of a typical length to width ratio of at least ten.
Narrow elongated pump lamps having a longitudinally disposed cavity to coaxially receive the lasing material have been described. Such coaxial pump lamps are relatively long compared to their width, and when correctly electrically excited, have relatively low pumping efficiency as the gaseous discharge material therein is likely to become ionized along a single, fibre-like path, emitting useful radiation over only a portion of the region surrounding the lasing material.
Alternative coaxial pump lamps have been described which are excited by RF induction methods, wherein the necessities of properly impedance matching the excitation field with the gas in the lamp generally results in a similarly elongated, shallow laser pump lamp.